by John Marshall Harlan, New York Company v. People of the State of New York…
“ We know from the face of the statute that it has a real, substantial relation to an object as to which the state is competent to legislate, namely, the personal security of those who are passengers on cars used within its limits. Why may not regulations to that end be made applicable, within a state, to the cars of railroad companies engaged in interstate commerce as well as to cars used wholly within such state? Persons traveling on interstate trains are as much entitled, while within a state, to the protection of that state, as those who travel on domestic trains. ”
